Ecosyste.ms: Advisories

Security Advisories: GSA_kwCzR0hTQS1tOGNnLXhjMnAtcjNmY84AAydr

rootless: `/sys/fs/cgroup` is writable when cgroupns isn't unshared in runc

Impact

It was found that rootless runc makes /sys/fs/cgroup writable in following conditons:

1. when runc is executed inside the user namespace, and the config.json does not specify the cgroup namespace to be unshared (e.g.., (docker|podman|nerdctl) run --cgroupns=host, with Rootless Docker/Podman/nerdctl)
2. or, when runc is executed outside the user namespace, and /sys is mounted with rbind, ro (e.g., runc spec --rootless; this condition is very rare)

A container may gain the write access to user-owned cgroup hierarchy /sys/fs/cgroup/user.slice/... on the host .
Other users's cgroup hierarchies are not affected.

Patches

v1.1.5 (planned)

Workarounds

• Condition 1: Unshare the cgroup namespace ((docker|podman|nerdctl) run --cgroupns=private). This is the default behavior of Docker/Podman/nerdctl on cgroup v2 hosts.
• Condition 2 (very rare): add /sys/fs/cgroup to maskedPaths

Permalink: https://github.com/advisories/GHSA-m8cg-xc2p-r3fc
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS1tOGNnLXhjMnAtcjNmY84AAydr
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Low
Classification: General
Published: over 1 year ago
Updated: over 1 year ago

CVSS Score: 2.5
CVSS vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:L

EPSS Percentage: 0.00044
EPSS Percentile: 0.14502

Identifiers: GHSA-m8cg-xc2p-r3fc, CVE-2023-25809
References:

• https://github.com/opencontainers/runc/security/advisories/GHSA-m8cg-xc2p-r3fc
• https://nvd.nist.gov/vuln/detail/CVE-2023-25809
• https://github.com/opencontainers/runc/commit/0d62b950e60f6980b54fe3bafd9a9c608dc1df17
• https://github.com/advisories/GHSA-m8cg-xc2p-r3fc

Repository: https://github.com/opencontainers/runc
Blast Radius: 11.1

Affected Packages